This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Various abbreviations that appear in the specification and/or in the drawing figures are defined as follows:
3GPPthird generation partnership projectUTRANuniversal terrestrial radio access networkEUTRANevolved UTRAN (LTE)LTElong term evolutionNode Bbase stationeNBEUTRAN Node B (evolved Node B)UEuser equipmentULuplink (UE towards eNB)DLdownlink (eNB towards UE)DCIdownlink control informationEPCevolved packet coreMMEmobility management entityS-GWserving gatewayMMmobility managementPHYphysicalRLCradio link controlMACmedium access controlRBresource blockPRBphysical resource blockPDCPpacket data convergence protocolO&Moperations and maintenanceCDMcode division multiplexingCQIchannel quality indicatorFDMAfrequency division multiple accessHARQhybrid automatic repeat requestACKacknowledgementNACKnegative ACKOFDMAorthogonal frequency division multiple accessSC-FDMAsingle carrier, frequency division multiple accessPMIPrecoding Matrix IndicatorPUCCHphysical uplink control channelPUSCHphysical uplink shared channelPCFICHphysical control format channelRel-8release 8RIRank IndicatorMIBmaster information blockSIBsystem information blockSRIscheduling request indicatorSRSsounding reference signalTTItransmission time intervalICICinter-cell interference coordinationACLRadjacent channel leakage ratioCMcubic metricZACZero AutoCorrelation
A communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA) has been under development within the 3GPP. In this system the DL access technique will be OFDMA, and the UL access technique will be SC-FDMA.
One specification of interest to these and other issues related to the invention is 3GPP TS 36.300, V8.5.0 (2008-05), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8), which is incorporated by reference herein in its entirety.
FIG. 4 reproduces FIG. 4-1 of 3GPP TS 36.300, and shows the overall architecture of the E-UTRAN system. The E-UTRAN system includes eNBs, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE. The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME (Mobility Management Entity) by means of a S1-MME interface and to a Serving Gateway (S-GW) by means of a S1-U interface. The S1 interface supports a many-to-many relation between MMEs/Serving Gateways and eNBs.
The eNB hosts the following functions:    functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);    IP header compression and encryption of user data stream;    selection of a MME at UE attachment;    routing of User Plane data towards Serving Gateway;    scheduling and transmission of paging messages (originated from the MME);    scheduling and transmission of broadcast information (originated from the MME or O&M); and    measurement and measurement reporting configurations for mobility and scheduling.
The PUCCH carries UL control information such as ACK/NACK (A/N), CQI, PMI, RI and a Scheduling Request Indicator (SRI). The PUCCH is used in the absence of UL data, and a single UE never transmits PUCCH simultaneously with PUSCH in LTE Rel. 8. FIG. 1 shows the logical split between different PUCCH formats and how the PUCCH is configured in the LTE specification. Reference can be made to 3GPP TS 36.211 V8.3.0 (2008-05), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8).
FIG. 1 shows the configuration of the PUCCH.
Different UEs are multiplexed on the PUCCH by means of CDM (i.e., CDM within the same resource block (RB)). Two basic PUCCH formats are supported in LTE Rel. 8 specifications, namely Format 1 and Format 2. Both formats use a cyclic shift of a ZAC sequence in each symbol (CDM in cyclic shift domain). Format 1 also utilizes block-wise spreading on top of the ZAC sequence (CDM using block spreading codes). PUCCH formats are used in the following manner:    Format 1: SRI    Format 1a: 1-bit A/N    Format 1b: 2-bit A/N    Format 2: Periodic CQI/PMI/RI    Format 2a: Periodic CQI/PMI/RI+1-bit A/N    Format 2b: Periodic CQI/PMI/RI+2-bit A/N
The PUCCH is configured using the following parameters (see 3GPP TS 36.211 for a complete list):                NRBHO The offset used for PUSCH frequency hopping, expressed in number of resource blocks (set by higher layers)        NRB(2) Bandwidth reserved for PUCCH formats 2/2a/2b, expressed in multiples of NscRB         Ncs(1) Number of cyclic shifts used for PUCCH formats 1/1a/1b in a resource block with a mix of formats 1/1 a/1b and 2/2a/2b        NscRB Resource block size in the frequency domain, expressed as a number of subcarriers (=12)        
Mapping of logical resource blocks (denoted as m) into physical resource blocks is shown in FIG. 2. Note that slot-based frequency hopping is always used on PUCCH.                nPRB Physical resource block number (index)        NRBUL Uplink bandwidth configuration, expressed in multiples of (NscRB=12)        
By configuration of the PUCCH reserved resources available PUSCH resources can be defined, as well as potential positions of the PRACH (to be within the PUSCH resource area).
Note that it has been decided that the sounding reference signal transmission can be semi-statically configured with respect to the bandwidth (within the PUSCH area).
The uplink bandwidth may be flexibly configured by applying PUCCH blanking as described in commonly owned and copending U.S. Provisional Patent Application No. 61/128,341, filed May 21, 2008 by Esa Tiirola, Kari Hooli, Kari Pajukoski and Sabine Rössel, entitled “Deployment Of LTE UL System For Arbitrary System Bandwidths via PUCCH Configuration”.
It has been agreed in 3GPP RAN WG#1 that in the LTE Rel-8 specifications a method for providing UL bandwidth flexibility, referred to as PUCCH blanking, is supported. Reference may be made to R1-084666, Change Request 36.211 CR 113, “Clarification to enable reuse of non-active PUCCH CQI RBs for PUSCH”, 3GPP TSG-RAN1 Meeting #55, Prague, Czech Republic, Nov. 10-14, 2008. The basic idea of PUCCH blanking is to over-dimension the PUCCH region, i.e., allocate more resources/PRBs to PUCCH usage than strictly required, and to leave the outermost PRBs unused. In this manner the UL bandwidth can be reduced symmetrically with respect to the center frequency to meet, for example, requirements of a certain operator. However, PUCCH blanking as defined in LTE Rel-8 reduces the achievable peak data rates of a single user, and may furthermore be problematic if the operator happens to have stringent requirements for emissions only on one side of the band.
A simple example of a common use case is shown in FIG. 3. The PUCCH is over-dimensioned by allocating 8 PRBs for the PUCCH (PRBs #0-4 and 12-15), and leaving the four outermost PRBs empty (two on each side). Since the resource allocation in LTE Rel-8 needs to be contiguous to maintain the SC properties, the maximum bandwidth that can be allocated to a single UE is reduced by 2 PRBs.
In FIG. 3 the neighboring band with stringent emission requirements is designated as “other band with emission limits” or as the “gray area”. In order to the meet the out-of-band emission requirements the LTE operator needs to reduce the UL system bandwidth by utilizing PUCCH blanking. In the example the two PRBs closest to the gray, non-LTE band are left empty. The symmetrical property of PUCCH blanking results in the active part of the PUCCH being shifted towards the center of the band, leaving the two outermost PRBs on the other side of the spectrum (PRB index 14 and 15) separated from the rest of the data PRBs. This situation has been referred to as PUSCH fragmentation.
Since in LTE Rel-8 the UL PUSCH allocations need to be contiguous, only 8 PRBs (PRB index 4-11) can be allocated to a single UE simultaneously for PUSCH transmission, even though there are two more PRBs available for the PUSCH. This situation results in a loss in terms of maximum bit rate per UE. In practical scenarios the number of blanked PRBs may be as great as 10-12, corresponding to a peak data rate loss of up to 12*144*6 bits/ms=10.4 Mbit/s.
As a solution to avoid spectrum fragmentation due to symmetrical PUCCH blanking, more flexible PUCCH allocation schemes have been presented in commonly owned and copending U.S. Provisional Patent Application No. 61/189,033, filed Aug. 15, 2008 by Carsten Ball, Sabine Rössel, Esa Tiirola, Kari Hooli, Kari Pajukoski and Miko Pesola, and entitled “Backward Compatible Physical Uplink Control Channel Resource Mapping”.
Reference may also be made to 3GPP TSG RAN WG4 (Radio) Meeting #48, R4-082027 Jeju Island, South Korea, 18 to 22 Aug. 2008, “Adjacent Channel UL/DL Co-existence”, Motorola.
Another technique to avoid the loss in peak data rates would be to allow for non-contiguous resource allocations in UL. This has been agreed to be included in the LTE-Advanced (sometimes referred to as Rel-10). These proposals assume that a new UL grant/DCI format is introduced, with no restrictions related to non-contiguous allocations (similar to some of the existing DL DCI formats). However, defining completely new resource allocation mechanisms and DCI formats is a rather long and involved process. Furthermore, defining new DCI formats does not necessarily solve the issue alone.
To at least overcome the problems discussed above, techniques are needed to at least maintain high peak data rates with PUCCH blanking.